I had been able to find more source code of OS/2 apps samples on older Shareware CD-ROMs.
I located that source code at github for everybody to have access to it: https://github.com/os2world
OS/2 Device Driver Web Presentation demos
Sample program to demonstrate sliders.
REDBOOK SAMPLE CODE: VOL. 1: CONTROL PROGRAM, REDBOOK SAMPLE CODE: VOL. 2: DOS & WINDOWS, EDBOOK SAMPLE CODE: VOL. 4: APPLICATION
PS/2 Roland MIDI driver source code
Demo code for programming Non-PM Graphics.
Demonstrate how to use the LS_OWNERDRAW listbox feature and to utilize that feature to highlite a keyword in any listbox item which is needed.
C Cross Reference Utility.
Combo Box Support Runtime. The routines in COMBOSUP.C are used to help set up combo boxes. They make it easy to add strings to the combo box's listbox, and to select the initial listbox item.
Dialog Box Usage Sample Source Code
FRACTINT plots and manipulates images of "objects" -- actually, sets of mathematical points -- that have fractal dimension.
A PM demo application of an screensaver of the Game of Life
SOS_utilities, sostree, findfile, ps.
Rob Hamerling's MAXIMUS DOWNload file SORT and list utility.
Kermit is a computer file transfer/management protocol and a set of communications software tools primarily used in the early years of personal computing in the 1980s
CIPHER is fairly simple to use yet provides excellent file security. It enrypts a file, making it unreadable junk until you decipher the file using the correct key.